There has been known an on-vehicle apparatus that receives in a diversity reception system a broadcasting signal modulated in an orthogonal frequency division multiplexing system (see Patent Document 1, for example). A plurality of receiving parts receive a broadcasting signal. A weighting value setting part sets a weighting value according to a signal level of each of the broadcasting signals received by the receiving parts. A signal combination part performs weighting processing by a weighting value set by the weighting value setting part on the respective broadcasting signals corresponding to respective carrier frequencies received by the receiving parts, and maximum-ratio-combines broadcasting signals obtained after the weighting processing. The weighting value setting part includes: an interference detection part; and a weighting value adjustment part. The interference detection part detects a carrier frequency containing noise from the received broadcasting signal. The weighting value setting part sets, as a weighting value to be applied to the carrier frequency detected by the interference detection part, a weighting value lower than the weighting value set according to the signal level.
There has been known an ICI amount estimation device that is included in a receiving device of a multicarrier signal and estimates an ICI amount in a carrier signal (see Patent Document 2, for example). A propagation path variation estimation unit calculates a variation amount of a propagation path frequency characteristic to output a propagation path variation characteristic. A fixity coefficient multiplying unit multiplies the propagation path variation characteristic by a fixity coefficient determined according to the predetermined number of carriers. The ICI amount estimation device estimates an ICI amount in each carrier based on the propagation path variation characteristic.
There has been known a receiving device including a plurality of antennas (see patent Document 3, for example). A plurality of synthesizing units generate weighting coefficients used for controlling amplitudes and phases of baseband signals only by the number of baseband signals by using band components different from one another out of individual baseband signals obtained by the plurality of antennas and multiply the individual baseband signals and the individual weighting coefficients together respectively, and then add these. A plurality of demodulation circuits, on synthesized signals output from the individual synthesizing units, perform fast Fourier transformation and perform demodulation processing based on an orthogonal frequency division multiplexing system for each subcarrier, and thereby generate amplitude and phase data. A carrier synthesizing unit synthesizes data output from the individual demodulation circuits for each subcarrier.
There has been known an OFDM diversity receiver having a plurality of reception branches that receive orthogonal frequency division multiplexing (OFDM) signals containing a plurality of subcarriers orthogonal to each other and output the received signals individually (see Patent Document 4, for example). An interference wave detection unit determines the presence and absence of an interference wave in each subcarrier of the received signals and estimates a first subcarrier group where interference waves exist and a second subcarrier group where no interference waves exist. A multiplying unit multiplies the first subcarrier group by a first weight used for eliminating the interference waves and multiplies the second subcarrier group by a second weight used for maximizing a signal-to-noise ratio. A combining unit combines output signals from the multiplying unit.
There has been known a receiving device for combining OFDM signals that receives an OFDM signal by a reception antenna composed of a plurality of array elements (see Patent Document 5, for example). A FFT unit transforms an OFDM signal received by the reception antenna into a reception carrier symbol in a frequency domain. An array combining unit weights and combines the reception carrier symbol by a first weighting coefficient for each subcarrier composing the OFDM signal to generate an array combined signal. A weighting coefficient optimizing unit generates a reference signal in which a transmission symbol has been estimated and generates a second weighting coefficient so that an error between the reference signal and the array combined signal may become minimum. A filter processing unit filters the reciprocal of the second weighting coefficient and then generates the re-reciprocal of the filtered reciprocal of the second weighting coefficient as a first weighting coefficient.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2010-226233
[Patent Document 2] Japanese Laid-open Patent Publication No. 2009-141740
[Patent Document 3] Japanese Laid-open Patent Publication No. 2006-217399
[Patent Document 4] Japanese Laid-open Patent Publication No. 2006-186421
[Patent Document 5] Japanese Laid-open Patent Publication No. 2011-188221
In radio communication, frequency selective fading caused by multipath occurs and reception quality deteriorates. Further, a spurious wave in a narrow-band is sometimes mixed in a frequency band of a reception signal. When power of a spurious wave becomes large to some extent with respect to a desired wave in a carrier unit, reception quality in a carrier with spurious waves deteriorates.